1. Field of the Invention
The present invention relates generally to computer network communications. More particularly, certain embodiments relate to internet protocol (IP) telephony in a packet switched network.
2. Background Art
Increasingly, network mobility allows communication devices capable of IP telephony to operate on behalf of a particular telephone service account at different times from different computer network access points and/or different geographic regions. Furthermore, telephony technologies increasingly allow such communication devices to operate on behalf of different telephone service accounts at different times and/or allow a particular service account to be serviced by different communication devices at different times. Therefore, the dynamic nature of IP network telephony results in frequent changes in the association between a particular telephone service account and a geographic location of a communication device operating on behalf of that particular telephone service account.
These dynamic changes pose a problem for services such as emergency telephone number (e.g. “911”) services, which rely on up-to-date geographic information to correctly dispatch emergency medical, police and/or fire services. To support access to emergency response services via IP telephony, IP networks usually rely on a central exchange—e.g. a voice over internet protocol (VoIP) private branch exchange (PBX)—which processes an IP telephony call placed to an emergency telephone number prior to sending call information on to the emergency telephone number service. Typically, the central exchange extracts from network packets of an emergency call a telephone number or other identifier of a telephone service account on whose behalf the emergency call was placed. A location service uses the extracted account identifier to retrieve geographic location information which is then included in the call to the emergency telephone number service.
Currently, updates related to certain device-specific location information are communicated in “end-to-end” data exchanges between the location service and the communication device whose location is to be determined by the location service. More particularly, these updates are exchanged via higher level communication protocols such as the Session Initiation Protocol (SIP). Operating, for example, at the Open Systems Interconnection (OSI) application layer 7, such protocols may communicate across one or more intermediary network nodes, wherein the communication device and the location service operate as a source sending and/or a destination receiving the location information update. The location service uses end-to-end communication to participate in separate respective message exchanges with each specific communication device in order to keep its location information up-to-date. As a result, the accuracy of the location service's information may, for example, be subject to temporary and/or intermittent unavailability of communication devices. Moreover, one or more intermediary network switching devices may have to relay multiple exchanges between communication devices and the location service—e.g. wherein the intermediary switching device itself does not participate in retrieving location information in response to an emergency call. Therefore, current techniques of providing location services for IP telephony may, for example, result in latent location information updates and/or network loading which reduces network performance.